Optimization Of Driving Control Strategy Of Capsule Robot In Bending Environment

As the direction and research focus of non-invasive interventional diagnosis and treatment, autonomous capsule robot can effectively inheriting and developing the advantages and the effect of passive capsule endoscope in clinical applications. With safety, reliability, and simple to operating, unlimited energy supplying and many other advantages, wireless magnetic driving capsule robot has become one of the most promising drive technology of autonomous capsule robot.At present, capsule robot research team of Dalian University of Technology has achieved turns swimming of capsule robot in a curved environment actuating by three-axis orthogonal Helmholtz coil system. On this basis, the paper studies the optimization of turning drive control strategy of capsule robot in bending environment, to improve the turning swimming performance of capsule robot and to reduce the unstable swing of capsule robot when it was turning.Firstly, a comprehensive evaluation index system has been built to evaluting turning swimming performance of capsule robot, which includes two indicators:turning average speed and turning average path deviation. Then, the multi-objective optimization problem (MOOP) was established to solving the optimal turning drive control strategy, based on the evaluation index system. The optimal value and the optimal solution of MOOP was obtained by use of fuzzy comprehensive evaluation method based on influence degree coefficient, the optimal steering angle and optimal driving distance was obtained finally.Then, the optimization of spatial direction of the magnetic vector was carried out, based on the solution of MOOP, inwhich will minimize the impact of the non-turning swing actution by swinging component of the magnetic moment when capsule robot was turning, while maintaining the turning effect of capsule robot unchanged, and to ensure that the size of the rotation drive torque was large enough to actuating capsule robot. The two rotation angles of space magnetic vector relative to initial direction of the magnetic vector as the decision variables of the optimization problem(OP), the optimal space magnetic vector direction was obtained by solving the OP by use of main objective method.Subsequently, non-contact trafficability of capsule robot and corresponding control strategies of universal rotating magnetic vector in circular arc tube and angle tube was studied, based on the geometric constraints of the the bending environment and the size of capsule robot. First, the steering position, steering angle and actuating distance for non-contact swimming of capsule robot in bending environment are derived based on path planning, for achieving successful steering control, based on aforementioned parameters, a spatial transformation model for directional adjustment of universal magnetic spin vector at each driving point is derived.Finally, an experimental platform composed by three-axis orthogonal Helmholtz coil system, three-phase inverter power adjusting device, petal-shaped capsule robot and curved pipe was set up. Verification experiments of optimal turning drive control strategy and non-contact trafficability of capsule robot was proposed. The experiment results show the improving effect of optimal turning drive control strategy to turning swimming performance of the capsule robot in bending environment, and effectiveness of the non-contact trafficability theory.